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OverUnity Research > Benches > PhysicsProf (Moderator: PhysicsProf) > Water electrolysis and heating with AC
2024-11-27, 16:46:31
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Author Topic: Water electrolysis and heating with AC  (Read 44710 times)
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img  muDped
Re: Water electrolysis and heating with AC « Reply #50 on: 2012-07-06, 19:02:30 »

Group: Tinkerer
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Posts: 3055
Good point.  When electrolyzing salt water it is
indeed possible to produce both Oxygen and
Chlorine at the positive plate under certain
conditions in varying proportions.

The electrolysis of salt water with suitable electrodes
able to stand up to the harsh conditions is
fascinating business.  In fact, it is big business.

The fireworks industry uses tons of chlorates
and perchlorates so produced annually.  Not to
mention the Chlorine Bleach for home use and
the Sodium or Potassium Hydroxide production.

The Wonderful World of ElectroChemistry!


---------------------------
For there is nothing hidden that will not be disclosed, and nothing concealed that will not be known or brought out into the open.
   
img  NickZ
Re: Water electrolysis and heating with AC « Reply #51 on: 2012-07-06, 22:16:30 »
Group: Guest
   Dumped:
   As you may have seen,  I've taken the liberty of re-posting your previous comments concerning the gas that is emitted from only one electrode,- back to Energetic Forums- Joule Ringer thread.  I hope that you don't mind, and I just wanted to let you know, in case you want to take a look to see the replies to your ideas.
   
                                                                                           NickZ
   
img  EMdevices
Re: Water electrolysis and heating with AC « Reply #52 on: 2012-07-06, 23:24:27 »
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Quote from: exnihiloest on 2012-07-01, 11:48:13
There are big problems with this formula vφ=c *√(2*ω*ε0)/σ.
1) the phase velocity tends to infinity when conductivity tends to zero
2) the phase velocity is frequency dependent
3) the order of magnitude is ridiculously small (< 1mm/s at 50 Hz)




yes you're right.

1)  this equation is applicable when σ is large (σ/ωε ≫ 1)  (the equation takes different forms depending on the conductivity levels, they specify that in the paper)
2)  yes, such a medium is called DISPERSIVE, becasuse different frequencies propagete with different velocities so a sharp pulse degrades and spreads out or disperses as it propagates.
3)  with good conductivity it is very small, but keep in mind that attenuation is also very small, so one wavelength would be about one skin depth perhaps.  Usually  you don't hear much talk of wavelength in a conductor becasue the attenuation is great near the interface, and skin depth is a much more usefull parameter.
   
img  muDped
Re: Water electrolysis and heating with AC « Reply #53 on: 2012-07-07, 02:45:41 »

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Posts: 3055
Quote from: NickZ
  ...I hope that you don't mind, and I just wanted to let you know, in case you want to take a look to see the replies to your ideas.

That is never a problem NickZ.  Anything which I may
opine into the public domain is for public use - no
permissions are necessary.

I've followed the discussion there and have noticed that
Seth has remarkable abilities and a natural talent towards
pedagogy.  His videos are well thought out and provide
great insights with unusual clarity.

I must add that both NickZ and LidMotor have contributed
greatly to the progress of the discussion.  Well done!


---------------------------
For there is nothing hidden that will not be disclosed, and nothing concealed that will not be known or brought out into the open.
   
img  exnihiloest
Re: Water electrolysis and heating with AC « Reply #54 on: 2012-07-07, 11:05:10 »
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Quote from: EMdevices on 2012-07-06, 23:24:27
...
2)  yes, such a medium is called DISPERSIVE, becasuse different frequencies propagete with different velocities so a sharp pulse degrades and spreads out or disperses as it propagates.

A dependence on the frequency sqrt is tremendous and totally incompatible with electrolyte properties. I don't know where the formula comes from but I never saw it in courses and it disagrees with the practice and good sense. May be the confusion comes from the speed of ions which is taken instead of the speed of the wave.

Quote
3)  with good conductivity it is very small, but keep in mind that attenuation is also very small, so one wavelength would be about one skin depth perhaps.  Usually  you don't hear much talk of wavelength in a conductor becasue the attenuation is great near the interface, and skin depth is a much more usefull parameter.

The skin depth applies for electrons in metals. Theoretically it could also apply for ions in solution (to be verified), but surely not at 50 Hz where the skin depth is much more than the width of the containers.
   
img  EMdevices
Re: Water electrolysis and heating with AC « Reply #55 on: 2012-07-07, 16:12:46 »
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Quote from: exnihiloest on 2012-07-07, 11:05:10
A dependence on the frequency sqrt is tremendous and totally incompatible with electrolyte properties. I don't know where the formula comes from but I never saw it in courses and it disagrees with the practice and good sense. May be the confusion comes from the speed of ions which is taken instead of the speed of the wave.

The skin depth applies for electrons in metals. Theoretically it could also apply for ions in solution (to be verified), but surely not at 50 Hz where the skin depth is much more than the width of the containers.



EX, you seem to be ignorant regarding this subject, and I'm surprised, because you are a HAM radio operator.

Have you not learned in your "courses" why communication with a submarine is difficult at higher frequencies?  It's because electromagnetic waves are attenuated rapidly due to the conductivity of the salt water, and how rapidly that happens is dependent on the frequency.  So the  skin depth is dependent on conductivity period, regardless if the charge carriers that enable it are electrons or not. 

I hope that helps

EM
   
img  exnihiloest
Re: Water electrolysis and heating with AC « Reply #56 on: 2012-07-09, 11:47:22 »
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Quote from: EMdevices on 2012-07-07, 16:12:46
EX, you seem to be ignorant regarding this subject, and I'm surprised, because you are a HAM radio operator.

Have you not learned in your "courses" why communication with a submarine is difficult at higher frequencies?  It's because electromagnetic waves are attenuated rapidly due to the conductivity of the salt water, and how rapidly that happens is dependent on the frequency.  So the  skin depth is dependent on conductivity period, regardless if the charge carriers that enable it are electrons or not. 

I hope that helps

EM

You missed the subtilities of the problems that I enounced.
"The skin depth applies for electrons in metals. Theoretically it could also apply for ions in solution (to be verified)": in metal, HF current flows much easier at the conductor surface than inside. In solutions, what is to verified is that there is a ionic current that flows better near and along the surface than deeper. Due to the losses caused by the water resistivity and to a different mobility of ions compared to electrons, the magnetic fields that force the electrons to move at the surface and are the source of the skin effect, are surely much weaker with ions. And for the same reasons, the problem of the transversal penetration of electromagnetic waves in water is different and only more or less related to the skin effect.

"the skin depth is much more than the width of the containers".
You talk about submarines many meters, tens or hundreds of meters under water! What applies to submarines because they are deeply immerged, doesn't apply to thin water widths likely thiner than the skin depth. In copper at 50 Hz, the skin depth is more than 9cm which is generally more than the distance between electrodes in electrolysis.

You should quantitatively rely theory to the physical context, by keeping in mind the order of magnitude of the effects, the direct causes of the effects, and the dimensions involved. A ham radio operator who is generally also a handyman, does it. Comments only qualitative are of poor help, they don't allow to face reality.
   
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